There are four standards for the wireless local network, which are IEEE802.11, IEEE802.11b and Bluetooth suitable for 2.4 GHz, and IEEE802.11a suitable for 5 GHz. If a wireless electronic device is used for various standards with different wireless frequency bands, a wide band antenna is necessary.
In one prior art for dual frequency antenna, an F type antenna is used for receiving signals from a first frequency and a second frequency. The antenna has a first plane conduction element and a second plane conduction element. The first plane conduction element is an L type structure and the second plane conduction element has a rectangular structure and is connected to and vertically to the first plane conduction element at a joint. The antenna is formed as a dipole antenna, in that the bandwidth, impedance matching and gain are adjusted by the shape of the first plane conduction element and second plane conduction element. However the area of the second plane conduction element will affect the gain of the antenna. If an antenna with higher gain is necessary, the area of a substrate thereof must be enlarged, but this is confined by the device space. Thus the area of the substrate can not be enlarged as desired.
Referring to FIG. 1, a schematic view about the super wide bandwidth antenna of the present invention. In that the prior art super wide bandwidth antenna has a first radiation portion 1A, a second radiation portion 1B and a ground portion 1C. Slits 100 are formed between the first radiation portion 1A and the second radiation portion 1B and between the second radiation portion 1B and the ground portion 1C. Although this kind of antenna can achieve the requirement of super wide bandwidth, it is illustrated that the electric properties are not stable. This can be got from the return lose. That, the area between the 3.5 GHz˜3.8 GHz has a return lose near −12 dB. It is easy to be bent or break as it is installed to an electronic device.